In recent years, it is necessary to shut electric waves in and out of buildings by surrounding with shielding material for protecting office information and for preventing mixing of communication lines, due to the progress of the communication systems such as portable telephone, wireless LAN, and the like.
However, the electromagnetic wave shielding materials which have been used only reflect the electromagnetic wave 100%, and the electromagnetic waves stored in a closed room have danger of inducing disturbance of communication lines and erroneous operation of electronic apparatuses. Especially, due to the progress of the semiconductor techniques in future, microelectronics and control systems made by applying them tend to show higher density, so that the disposition of the reflected electromagnetic waves in tightly closed spaces is a subject still to be settled.
As a means of preventing these obstacles caused by the reflection of electromagnetic wave, there is known a wave absorbing material having a coating layer dispersing ferrite in an organic polymer. However, in order for such electromagnetic wave absorbing material to obtain practically effective absorbing capacity, there is necessitated a thick film of more than 2 mm, and the medium becomes a heavy product of more than 8 Kg/m.sup.2. Accordingly, when such material is applied to a building, the strength of the whole building has to be increased to support such product, with requirement of high cost. It also associates various problems for the work of adhering it onto a wall surface and the like.
To cope with the above, Japanese Patent Laid-open Publication No. 6-140787/1994 proposes that a ferrite and carbon powder dispersed resin layer is sandwiched between an electric wave reflecting layer and an electroconductive pattern. However, it also has limitation in reduction of weight, because of the large specific gravity of ferrite.
In addition, construction of multi-storied buildings gives rise to a problem in occurrence of TV ghost. To solve the problem, there are required low frequency of the subjective electric wave and high absorbing capacity, so that a 6-8 mm ferrite sintered medium is applied to the buildings. Its weight is more than 40 kg/m.sup.2, and it is very difficult to make the structure to withstand such a heavy weight. It is more difficult to build higher storied buildings, which requires enormous building cost. Accordingly, the development of electric wave absorbing material having light weight and high absorbing capacity is desired.